176 ACTION OF GASES AND OF THE 



others that certain species of bacteria cause an abundant evolution 

 of H 2 S as a result of their development in an albuminous medium 

 (Bacillus sulfureus and Proteus sulfureus). 



Sulphur Dioxide, SO 2 . Very numerous experiments have been 

 made with this gas, owing to the fact that it has been extensively 

 used in various parts of the world for the disinfection of hospitals, 

 ships, apartments, clothing, etc. 



In the writer's experiments, made in 1880, dry vaccine virus on 

 ivory points was disinfected by exposure for twelve hours in an at- 

 mosphere containing one volume per cent of this gas, and liquid 

 virus, exposed in a watch glass, by one-third of this amount. Sub- 

 sequent experiments (1885) showed that pus micrococci were killed 

 by exposure for eighteen hours in a dry atmosphere containing twenty 

 volumes per cent of SO 2 , but that four volumes per cent failed. In 

 the presence of moisture this gas has considerably greater germicidal 

 power than this, owing, no doubt, to the formation of the more ac- 

 tive agent, sulphurous acid (H 2 SO 3 ). But in a pure state anhydrous 

 sulphur dioxide does not destroy spores. The writer has shown that 

 the spores of Bacillus anthracis and Bacillus subtilis are not killed by 

 contact for some time with liquid SO 2 (liquefied by pressure). Koch 

 exposed various species of spore-bearing bacilli in a disinfection cham- 

 ber for ninety-six hours, the amount of SO 2 at the outset of the ex- 

 periment being 6.13 volumes per cent, and at the end 3.3 per cent. 

 The result was entirely negative. 



But in the absence of spores the anthrax bacillus, in a moist con- 

 dition, attached to silk threads, was destroyed in thirty minutes in 

 an atmosphere containing one volume per cent. 



In another of Koch's experiments the amount of SO 2 in the disin- 

 fection chamber was at the outset 0.84 per cent, and at the end of 

 twenty-four hours 0.55 per cent. An exposure of one hour in this at- 

 mosphere killed anthrax bacilli attached to silk threads, in a moist 

 .condition; but four hours' exposure failed to kill Bacillus prouigiosus 

 growing on potato, while twenty-four hours' exposure was successful. 

 A similar result was obtained with Bacillus pyocyaneus. 



Thinot, as a result of experiments made in 1890, arrives at the 

 conclusion that the specific germs of tuberculosis, glanders, farcy of 

 cattle, typhoid fever, cholera, and diphtheria are destroyed by twenty- 

 four hours' exposure in an atmosphere containing SO 2 developed by 

 the combustion of sixty grains of sulphur per cubic metre. This 

 amount corresponds closely with that fixed by the Committee on Dis- 

 infectants of the American Public Health Association on the experi- 

 mental evidence obtained by the writer in 1885. But the committee 

 insisted upon the presence of moisture and made the time of exposure 

 twelve hours "exposure for twelve hours to an atmosphere con- 



